How to configure and use OpenSSH on CentOS 7

Secure Shell or SSH is a protocol which allows users to connect to a remote system using a client-server architecture.

The login session is encrypted and very secure. Today we are going to show you how to configure and use OpenSSH on a Linux VPS using CentOS 7 as an operating system.
CentOS 7 provides openssh, openssh-server and openssh-clients packages. The openssh package requires openssl-libs to be installed on the system since it provides some very important cryptographic libraries.

If you order a Linux VPS with us you will have all these packages installed on your server. If not, you will need to install them manually.

For that purpose you can use the following command:

# yum install openssh openssh-server openssh-clients openssl-libs

Once the packages are installed you are ready to connect to the server via SSH. The default configuration file for the sshd daemon is /etc/ssh/sshd_config and most of the settings for the daemon are defined in this file. Before making any changes, it is recommended to make a copy of the original configuration file so if you experience some problem you can revert the changes back the the default.

# cp /etc/ssh/sshd_config /etc/ssh/sshd_config.orig

To view and edit the configuration file you can use a text editor of your choice. We are going to use nano because of its simplicity.

# nano /etc/ssh/sshd_config

The first thing you might like to change is the listening port number. By default, the SSH daemon listens on port 22 and for security reasons you can change the number to something else. Change the line:

Port 22

to

Port 2022

You can use a port number of your choice which is not used by some other service on your CentOS VPS. Once you make the changes you can save and close the file. In order the changes to take effect, you should restart the SSH daemon.

# systemctl restart sshd.service

To improve the security even further, it is recommended to use key-based authentication. Key-based authentication will allow you to connect to your server via SSH without using the password of your system user. Instead, you will need use SSH keys. For more information about how to log in via SSH without password using SSH keys we recommend you to read our dedicated tutorial.

The SSH protocol allows other operations like copying files between two remote hosts to be completed in an encrypted and secure way. For that reason, you can use scp, a remote file copy program, and sftp which is an interactive file transfer program very similar to FTP. For more information on how to use scp and sftp you can read the user manual which is available at http://www.openssh.com/manual.html. We will cover this topic in some of our next Linux based tutorials.

Of course you don’t have to do any of this if you use one of our Linux VPS hosting services, in which case you can simply ask our expert Linux admins to help you with the OpenSSH setup. They are available 24×7 and will take care of your request immediately.

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